class Base64MimeHeaderEncoder

final class Base64MimeHeaderEncoder extends Base64Encoder implements MimeHeaderEncoderInterface {
    public function getName() : string {
        return 'B';
    }
    
    /**
     * Takes an unencoded string and produces a Base64 encoded string from it.
     *
     * If the charset is iso-2022-jp, it uses mb_encode_mimeheader instead of
     * default encodeString, otherwise pass to the parent method.
     */
    public function encodeString(string $string, ?string $charset = 'utf-8', int $firstLineOffset = 0, int $maxLineLength = 0) : string {
        if ('iso-2022-jp' === strtolower($charset)) {
            $old = mb_internal_encoding();
            mb_internal_encoding('utf-8');
            $newstring = mb_encode_mimeheader($string, 'iso-2022-jp', $this->getName(), "\r\n");
            mb_internal_encoding($old);
            return $newstring;
        }
        return parent::encodeString($string, $charset, $firstLineOffset, $maxLineLength);
    }

}